diff --git a/.github/workflows/build-wheel-tree.yaml b/.github/workflows/build-wheel-tree.yaml
index 7cf93ed..e53c513 100644
--- a/.github/workflows/build-wheel-tree.yaml
+++ b/.github/workflows/build-wheel-tree.yaml
@@ -4,7 +4,7 @@ on:
     branches:
       - main
     tags:
-      - '**'
+      - "**"
   pull_request:
 
 concurrency:
@@ -25,7 +25,7 @@ jobs:
           fetch-depth: 0
 
       - name: Create venv
-        run: /opt/python/cp38-cp38/bin/python3 -m venv venv
+        run: /opt/python/cp310-cp310/bin/python3 -m venv venv
 
       - name: Create Wheels
         run: |
diff --git a/.github/workflows/build-wheels.yaml b/.github/workflows/build-wheels.yaml
index 00aca57..fbd686a 100644
--- a/.github/workflows/build-wheels.yaml
+++ b/.github/workflows/build-wheels.yaml
@@ -32,7 +32,7 @@ jobs:
           fetch-depth: 0
 
       - name: Create venv
-        run: /opt/python/cp38-cp38/bin/python3 -m venv venv
+        run: /opt/python/cp310-cp310/bin/python3 -m venv venv
 
       - name: Create Wheel
         run: |
diff --git a/hsms/clvm_serde/__init__.py b/hsms/clvm_serde/__init__.py
index cd4a121..093e93c 100644
--- a/hsms/clvm_serde/__init__.py
+++ b/hsms/clvm_serde/__init__.py
@@ -1,4 +1,5 @@
-from dataclasses import is_dataclass, fields, MISSING
+from dataclasses import MISSING, fields, is_dataclass
+from types import UnionType
 from typing import Any, Callable, Optional, Tuple, Type, Union, get_type_hints
 
 from chia_base.meta.type_tree import ArgsType, CompoundLookup, OriginArgsType, TypeTree
@@ -115,6 +116,7 @@ def ser(item):
     tuple: serialize_for_tuple,
     tuple_frugal: ser_for_tuple_frugal,
     Union: serialize_for_optional,
+    UnionType: serialize_for_optional,
 }
 
 
@@ -342,6 +344,7 @@ def deserialize_optional(p: Program):
     tuple: deser_for_tuple,
     tuple_frugal: de_for_tuple_frugal,
     Union: deser_for_optional,
+    UnionType: deser_for_optional,
 }
 
 
diff --git a/tests/test_clvm_serde.py b/tests/test_clvm_serde.py
index ea05159..6a58740 100644
--- a/tests/test_clvm_serde.py
+++ b/tests/test_clvm_serde.py
@@ -31,7 +31,8 @@
 from .legacy.unsigned_spend import UnsignedSpend as LegacyUS
 
 
-def test_ser():
+@pytest.mark.parametrize("pep604", [True, False])
+def test_ser(pep604: bool):
     tpb = to_program_for_type(bytes)
     fpb = from_program_for_type(bytes)
     tps = to_program_for_type(str)
@@ -134,9 +135,16 @@ class Foo:
         f1 = fp(p)
         assert f1 == foo
 
-    @dataclass
-    class Foo:
-        a: Optional[int] = field(metadata=dict(key="a"))
+    if pep604:
+
+        @dataclass
+        class Foo:
+            a: int | None = field(metadata=dict(key="a"))
+    else:
+
+        @dataclass
+        class Foo:
+            a: Optional[int] = field(metadata=dict(key="a"))
 
     tp = to_program_for_type(Foo)
     fp = from_program_for_type(Foo)
@@ -151,9 +159,16 @@ class Foo:
     p1 = tp(foo)
     assert p1 == p
 
-    @dataclass
-    class Foo:
-        a: Optional[List[int]] = field(metadata=dict(key="a"))
+    if pep604:
+
+        @dataclass
+        class Foo:
+            a: List[int] | None = field(metadata=dict(key="a"))
+    else:
+
+        @dataclass
+        class Foo:
+            a: Optional[List[int]] = field(metadata=dict(key="a"))
 
     tp = to_program_for_type(Foo)
     fp = from_program_for_type(Foo)